This research concerns the structure of the apoprotein (apoB) of human plasma low density lipoprotein (LDL). ApoB has been solubilized in 6M guanidine and, following delipidation, the protein is being characterized in terms of its physical and immunologic properties as well as being fingerprinted. Using these techniques apoB from various subjects and from VLDL as well as LDL will be studied to examine the question of apoprotein isomorphism. Having developed methods of working with delipidated apoB in solution we are also investigating the properties of the apoprotein in the presence and absence of lipid, gathering preliminary data in preparation for reconstitution studies.